In early 1990s, Dow Corporation disclosed [Me2Si(Me4C5)NtBu]TiCl2 (Constrained-Geometry Catalyst, hereinafter abbreviated as CGC) in U.S. Pat. No. 5,064,802, and the superiority of CGC in a copolymerization reaction of ethylene and alpha-olefin compared to existing metallocene catalysts known in the art is mainly summarized into two points as follows: (1) a polymer having a high molecular weight while exhibiting high activity even at a high polymerization temperature is produced, and (2) copolymerizability of alpha-olefin having high steric hindrance such as 1-hexene and 1-octene is highly superior. In addition to these, various properties of CGC have been gradually known in polymerization reactions, and as a result, efforts to synthesize derivatives of CGC to use these as a polymerization catalyst have been actively made in both academics and industries.
As one approach among these efforts, synthesis of metal compounds in which other various bridges and nitrogen substituents are introduced instead of a silicon bridge, and polymerization of these metal compounds have been tried. The representative metal compounds that have been known till recently are the following Compounds (1) to (4) (Chem. Rev. 2003, 103, 283).

In Compounds (1) to (4), phosphorous (1), ethylene or propylene (2), methylidene (3), and methylene (4) bridges are introduced, respectively, instead of a silicon bridge having a CGC structure, however, improved results compared to CGC have not been obtained in terms of activity or copolymerization efficiency when used in ethylene polymerization or copolymerization with alpha-olefin.
Furthermore, as another approach, compounds formed with oxido ligands instead of amido ligands of CGC have been actively synthesized, and polymerization using these compounds also haven been partly tried. Examples thereof are summarized as follows.

Compound (5) was reported by T. J. Marks et al. and in the compound, a cyclopentadiene (Cp) derivative and an oxido ligand are cross-linked by an ortho-phenylene group (Organometallics 1997, 16, 5958). Compounds having the same cross-linking and polymerization using these were also reported by Mu et al. (Organometallics 2004, 23, 540). In addition, the indenyl ligand and the oxido ligand being cross-linked by the same ortho-phenylene group was reported by Rothwell et al. (Chem. Commun. 2003, 1034). Compound (6) was reported by Whitby et al., and in the compound, a cyclopentadienyl ligand and an oxide ligand are crossed by 3 carbons (Organometallics 1999, 18, 348), and these catalysts were reported to exhibit activities for syndiotactic polystyrene polymerization. Similar compounds were also reported by Hessen et al. (Organometallics 1998, 17, 1652). Compound (7) was reported by Rau et al., and the compound shows an activity for ethylene polymerization and ethylene/1-hexene copolymerization at a high temperature and high pressure (210° C., 150 mPa) (J. Organomet. Chem. 2000, 608, 71). After that, synthesis of catalysts having similar structures (8) and high-temperature and high-pressure polymerization using these catalysts were applied for a patent by Sumitomo Corporation (U.S. Pat. No. 6,548,686). However, among the attempts described above, only a small number of catalysts are practically used in commercial plants. Accordingly, catalysts showing more improved comprehensive performances have been required, and simple methods for preparing these catalysts have been required as well.